RESUMO
Sessile organisms, such as plants, developed various ways to sense and respond to external and internal stimuli to maximize their fitness through evolutionary time. Transcripts and protein regulation are, among many, the main mechanisms that plants use to respond to environmental changes. SKIP protein is one such, presenting an SNKW interacting domain, which is highly conserved among eukaryotes, where SKI interacting protein acts in regulating key processes. In the present work, many bioinformatics tools, such as phylogenetic relationships, gene structure, physical-chemical properties, conserved motifs, prediction of regulatory cis-elements, chromosomal localization, and protein-protein interaction network, were used to better understand the genome-wide SNW/SKIP domain-containing proteins. In total, 28 proteins containing the SNW/SKIP domain were identified in different plant species, including plants of agronomic interest. Two main protein clusters were formed in phylogenetic analysis, and gene structure analysis revealed that, in general, the coding region had no introns. Also, expression of these genes is possibly induced by abiotic stress stimuli. Primary structure analysis of the proteins revealed the existence of an evolutionarily conserved functional unit. But physicochemical properties show that proteins containing the SNW/SKIP domain are commonly unstable under in vivo conditions. In addition, the protein network, demonstrated that SKIP homologues could act by modulating plant fitness through gene expression regulation at the transcriptional and post-transcriptional levels. This could be corroborated by the expression number of gene copies of SKIP proteins in many species, highlighting it's crucial role in plant development and tolerance through the course of evolution.
Assuntos
Genoma de Planta , Filogenia , Proteínas de Plantas , Plantas , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas/genética , Plantas/metabolismo , Domínios Proteicos , Regulação da Expressão Gênica de PlantasRESUMO
BACKGROUND AND OBJECTIVE: Periodontal diseases are associated with bacterial challenge and the host immune response, and are also modulated by genetic factors. There is evidence that sickle cell anaemia (SCA) does not represent a risk factor for periodontal diseases. However, it is still unclear whether the heterozygous condition [sickle cell trait (SCT)] is associated with periodontal diseases. SCT is a genetic condition that can cause vaso-occlusive events, which may be associated with a propensity to bacterial infections. The aim of this study was to investigate the association of SCA and SCT with periodontal diseases by evaluating clinical and radiographic characteristics. MATERIAL AND METHODS: The sample (n = 369) was selected and divided into two groups: exposed groups [HbSS (SCA genotype) and HbAS (SCT genotype) = 246] and a nonexposed group (HbAA = 123). HbAA consisted of individuals without SCA and SCT. The clinical parameters evaluated were plaque index, gingival index, calculus index, clinical probing depth, clinical attachment level, gingival recession, tooth mobility and furcation involvement. The percentage of alveolar bone loss was measured using a Schei ruler. Binomial and Poisson regressions were used to estimate correlations of interest (α = 0.05). RESULTS: None of the periodontal parameters was associated with SCA. SCT was associated with gingivitis (p = 0.041) and periodontitis (p = 0.002). Individuals with SCT had a lower plaque index (p = 0.044) but a higher calculus index (p = 0.003) and greater alveolar bone loss (p = 0.010) compared with subjects in the HbAA group. CONCLUSIONS: SCT can act as a predictor for establishment of periodontal diseases. There was no correlation between SCA and periodontal diseases.
Assuntos
Anemia Falciforme/complicações , Anemia Falciforme/imunologia , Doenças Periodontais/complicações , Doenças Periodontais/imunologia , Traço Falciforme/complicações , Traço Falciforme/imunologia , Adolescente , Adulto , Perda do Osso Alveolar/complicações , Anemia Falciforme/genética , Brasil , Criança , Pré-Escolar , Estudos de Coortes , Cálculos Dentários , Índice de Placa Dentária , Feminino , Genótipo , Retração Gengival/complicações , Gengivite/complicações , Hemoglobina A/análise , Hemoglobina Falciforme/análise , Humanos , Masculino , Pessoa de Meia-Idade , Perda da Inserção Periodontal/complicações , Índice Periodontal , Bolsa Periodontal/complicações , Periodontite/complicações , Periodontite/imunologia , Fatores de Risco , Traço Falciforme/genética , Mobilidade Dentária/complicaçõesRESUMO
Ceria (CeO2) is a promising dilute magnetic semiconductor. Several studies report that the intrinsic and extrinsic structural defects are responsible for room temperature ferromagnetism in undoped and transition metal doped CeO2 nanostructures; however, the nature of the kind of defect necessary to promote and stabilize the ferromagnetism in such a system is still a matter of debate. In the work presented here, nanorods from the system Ce1-xCuxO2-δ with x = 0, 0.01, 0.03, 0.05 and 0.10, with the more stable {111} surface exposed were synthesized by a microwave-assisted hydrothermal method. A very careful structure characterization confirms that the Cu in the samples assumes a majority 2+ oxidation state, occupying the Ce (Ce(4+) and Ce(3+)) sites with no secondary phases up to x = 0.05. The inclusion of the Cu(2+) in the CeO2 structure leads to the introduction of oxygen vacancies in a density proportional to the Cu(2+) content. It is supposed that the spatial distribution of the oxygen vacancies follows the Cu(2+) distribution by means of the formation of a defect complex consisting of Cu(2+) ion and an oxygen vacancy. Superconducting quantum interference device magnetometry demonstrated a diamagnetic behavior for the undoped sample and a typical paramagnetic Curie-Weiss behavior with antiferromagnetic interactions between the Cu(2+) ions for the single phase doped samples. We suggest that the presence of oxygen vacancies is not a sufficient condition to mediate ferromagnetism in the CeO2 system, and only oxygen vacancies in the surface of nanostructures would lead to such a long range magnetic order.
RESUMO
The effects of NaCl 0.9%, Ringer-acetate, and Ringer-dextran given as intravenous infusions in the microcirculatory changes observed in early stages of endotoxemia were investigated in male hamsters treated with Escherichia coli lipopolysaccharide (LPS). The cheek pouch was studied in vivo by means of intravital microscopy. Mean arterial (MAP) and venous pressures (CVP), heart rate, mean arteriolar internal diameter, spontaneous arteriolar vasomotion (AV), red blood cell velocity (RBCV) in these vessels, and long-term effects of LPS were evaluated in animals treated with either LPS alone or the combination of LPS with NaCl 0.9%, Ringer-acetate and Ringer-dextran. The intravenous injection of LPS (0.3 mg/kg) elicited a significant reduction in MAP and CVP, cessation of AV and a decrease in RBCV. In our study, the heart rate and the arteriolar diameter did not change significantly, compared with the control values obtained before the LPS injection. No improvement in the MAP could be detected with infusions of NaCl 0.9% or Ringer-acetate but the infusion of Ringer-dextran increased it significantly. All infusions tested maintained the CVP until the end of the observation period and the Ringer-dextran increased it significantly. The heart rate was maintained around 360 beats/min with a tendency to decrease 70 min after the LPS infusion in all groups studied except the group which received NaCl 0.9% where the heart rate decreased significantly. In all the four groups, the mean arteriolar diameter did not change significantly with time during the observed period. RBCV decrease with the combination LPS + NaCl 0.9% and the infusions of Ringer-acetate and Ringer-dextran maintained it until the end of the observation period. The combination of LPS + NaCl 0.9% maintained the spontaneous arteriolar vasomotion during 50 min after LPS injection and the infusion of Ringer-acetate maintained it for the 3-h observation period. The infusion of Ringer-dextran maintained the amplitude of the spontaneous arteriolar vasomotion and increased its frequency significantly. The long-term effects of LPS showed weight loss and pus on the periorbital area. Our results suggest that the best solution to maintain the microcirculatory parameters during the early stage of endotoxemia after LPS injection was the Ringer-dextran.
Assuntos
Bochecha/irrigação sanguínea , Dextranos/farmacologia , Soluções Isotônicas/farmacologia , Lipopolissacarídeos/toxicidade , Animais , Arteríolas/anatomia & histologia , Arteríolas/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Cricetinae , Modelos Animais de Doenças , Edema/tratamento farmacológico , Eritrócitos/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Masculino , Mesocricetus , Microcirculação/efeitos dos fármacos , Solução de Ringer , Redução de PesoRESUMO
Endotoxin given intravenously is known to cause plasma leakage and subsequent loss of circulating plasma volume. Hypertonic saline resuscitation has been successfully applied in hemorrhagic and traumatic shock, but its application for the treatment or prevention of septic or endotoxin shock is less well studied. Our aim was to investigate the effects of endotoxin on plasma leakage in hamsters when administered in two different ways: applied locally to the hamster cheek pouch microcirculation or systemically by i.v. injection. The cheek pouch was studied by intravital microscopy using FITC-labeled dextran as a tracer of plasma leakage. Escherichia coli lipopolysaccharide (LPS) was continuously added into the superfusion buffer of the cheek pouch preparation during 120 min in two control groups (each n = 6) and two further groups (each n = 6) treated with either hypertonic saline (HS) or hypertonic saline and dextran (HSD). Treatment was given as an i.v. injection 0.35 mL NaCl 7.5%/100 g b.w. during 4 min starting 15 min prior to the start of endotoxin application. Endotoxin caused a reversible increase in the number of postcapillary venular leaks with a maximal response at 70 min after start of endotoxin application. The maximal responses were reduced to 36% in the HS-treated and to 37% in the HSD-treated group in comparison to what was seen in the control groups. In the second part of the study endotoxin was given i.v. 0.3 mg/kg to anesthetized hamsters (n = 41) and arterial blood samples were collected at 0, 60, 120, and 180 min after endotoxin injection for measurement of hematocrit and plasma FITC-dextran concentration. Hamsters were divided into seven groups: untreated control group (n = 6); HSC control group given only an i.v. injection of hypertonic saline (n = 6); LPS group given endotoxin 0.3 mg/kg during 1 min (n = 9); HSp group given hypertonic saline (NaCl 7.5%) 10 min prior to i.v. endotoxin (n = 6); HSa group given hypertonic saline 10 min after i.v. endotoxin (n = 6); HSD group given hypertonic saline with dextran 40, 10 min prior to i.v. endotoxin (n = 6); HSD control group given only i.v. hypertonic saline + dextran and no endotoxin (n = 2). Injection of endotoxin caused a significant increase in hematocrit, which was counteracted by hypertonic saline treatment, with or without dextran, probably due to reduced extravasation of plasma in postcapillary venules.
Assuntos
Permeabilidade Capilar/efeitos dos fármacos , Dextranos/administração & dosagem , Endotoxinas/toxicidade , Substitutos do Plasma/administração & dosagem , Volume Plasmático/efeitos dos fármacos , Solução Salina Hipertônica/administração & dosagem , Choque Séptico/prevenção & controle , Choque Séptico/fisiopatologia , Animais , Cricetinae , Injeções Intravenosas , Choque Séptico/induzido quimicamenteRESUMO
The purpose of the present study was to verify the correspondence between the administrative experience of the Hospital "Sofia Feldman" and the theory on flexible management proposed by MOTTA (1991) and MEDICI & SILVA (1993). It also described innovation elements for institutional integration with the community, such as the substitute mother, ombudsman and systematic voluntary work, done by Community Association of Friends and Users of Sofia Feldman Hospital. Data were collected with a semi-structured interview, applied to employees of different sectors, aiming at knowing their perception about the administrative model used. The flexible administration characteristics of the hospital were evidenced, however authors found elements of classical administration.
Assuntos
Administração Hospitalar/métodos , Brasil , HumanosRESUMO
The parasitic specificity of larval, nymph and adult Amblyomma cajennense on six different host species: Oryctolagus cuniculus, Rattus norvegicus, Gallus gallus domesticus, Anas platyrhynchus, Coturnix coturnix and Streptopelia decorata is described. In terms of the numbers of larvae and nymphs recovered, O. cuniculus was the best host species. The modal day for drop-off of larvae and nymphs was day three for the mammal hosts, but variable in the birds. We conclude that adult A. cajennense have a strong degree of specificity due to the fact that the tick failed to complete its life cycle on any of the evaluated hosts. The immature stages, on the other hand, showed a low level of specificity, most especially in the larval stage, indicating the existence of secondary hosts which probably serve as dispersers in the wild. The results also indicated a variable drop-off rhythm for larvae and nymphs in two periods, diurnal (6-18 hr) and nocturnal (18-6 hr), which differed depending upon the host.
Assuntos
Interações Hospedeiro-Parasita/fisiologia , Carrapatos/fisiologia , Adulto , Animais , Aves/parasitologia , Feminino , Humanos , Larva/fisiologia , Ninfa/fisiologia , Coelhos/parasitologia , Ratos/parasitologia , Especificidade da Espécie , Fatores de TempoRESUMO
BACKGROUND: The extracellular matrix (ECM) has important roles in prostatic development, and marked stromal changes take place in the rat ventral prostate (VP) after androgen deprivation. However, little knowledge exists about individual ECM components. METHODS: The distribution of elastic fibers (EF) and elastic-related fibers (ERF) in the VP of castrated and control rats was investigated, using histochemistry and transmission electron microscopy (TEM). RESULTS: EF are barely detected in the prostatic stroma, but ERF are relatively abundant. Castration results in a relative increase in the number and thickness of ERF. TEM showed an open network of ECM microfibrils throughout, the stroma and thin and short EF, which increase in number and thickness after orchiectomy. CONCLUSIONS: The presence of elastic system components in the rat VP warrants the deformability required for the secretion exclusion under the action of smooth muscle cells, and the castration-induced modification may be related to the contraction of the tissue and maintenance of peculiar arrangements of other ECM components.
Assuntos
Elastina/análise , Orquiectomia , Próstata/química , Animais , Histocitoquímica , Masculino , Microscopia Eletrônica , Ratos , Ratos Wistar , Fatores de TempoRESUMO
This study focuses on the basement membrane associated modifications that take place after androgen blockade, by studying some of its main components, through histochemical, immuno-histochemical and Western blotting tests, and its ultrastructural aspects. It was demonstrated that laminin and collagen type IV remain associated with a thickened basement membrane and that there is an apparent increase in heparan sulfate content 21 days after castration. Ultrastructurally, basal lamina appeared extensively folded and pleated. It was also observed that detachment of epithelial cells is not dependent of basal lamina degradation and that the free basal lamina surfaces are folded by the action of adjacent cells. We have also observed some aspects of smooth muscle cell degeneration and death, that lead to modifications of the associated basal lamina. In this case, residual basal lamina also shows extensive folding. The results suggested that degradation of excess basement membrane does not occur or is a very slow process within the period examined, and that basement membrane is left re-organized but ultrastructurally and compositionally unaffected.
Assuntos
Androgênios/fisiologia , Membrana Basal/ultraestrutura , Próstata/citologia , Animais , Membrana Basal/química , Colágeno/análise , Glicosaminoglicanos/análise , Laminina/análise , Masculino , Orquiectomia , Próstata/ultraestrutura , Ratos , Ratos WistarRESUMO
We have studied the possibility of associating fluorescence microscopy and hematoxylin-eosin staining for the identification of elastic fibers in elastin-rich tissues. Elastic fibers and elastic laminae were consistently identified by the proposed procedure, which revealed itself to be easy and useful for the determination of such structures and their distribution. The fluorescence properties of stained elastic fibers are due to eosin staining as revealed by fluorescence analysis of the dye in solution, with no or only minor contribution by the elastin auto-fluorescence. The main advantage of this technique resides in the possibility of studying the distribution of elastic fibers in file material without further sectioning and staining. The use of the confocal laser scanning microscope greatly improved the resolution and selectivity of imaging elastic fibers in different tissues. The determination of the three-dimensional distribution and structure of elastic fiber and laminae using the confocal laser scanning microscope was evaluated and also produced excellent results. used to discriminate calcified bone and elastic fibers using the fluorescence microscope (Bradbeer et al. 1994). The selective fluorescence exhibited by these two main tissue components is based on the very faint eosin staining, while intensely eosinophilic substrates and those stained with the highly absorbing basic dyes show no fluorescence or just a very faint signal. Considering the possibility of using eosin fluorescence for the selective identification of some tissue components, we have extended this approach to the study of elastic fibers in hematoxylin-eosin (H&E) preparations. This paper then describes the results of observations with the fluorescence microscope of some H&E stained sections and evaluates the use of the confocal laser scanning microscope to image elastic fibers in the same preparations. Furthermore, we have also studied absorption and fluorescence spectra of eosin and phloxine, a closely related dye, in solution, to correlate them with the fluorescence detected in tissue sections.
Assuntos
Tecido Elástico/química , Microscopia Confocal/métodos , Microscopia de Fluorescência/métodos , Animais , Aorta/química , Amarelo de Eosina-(YS) , Hematoxilina , Humanos , Lasers , Mamíferos , Mesentério/química , Pele/química , Coloração e RotulagemRESUMO
This study focuses on the use of hematoxylin-eosin staining plus fluorescence microscopy for the investigation of elastic fibers in some elastic cartilages. We have observed that elastic fibers are consistently imaged by the proposed procedure and the resolution attained is similar to that obtained with the classical Weigert's fuchsin-resorcin. The results also demonstrate that elastin autofluorescence gives little or no contribution to the final fluorescence and that the use of the confocal laser scanning microscope adds to the resolution, permits the use of thicker sections and reveals of minute structural at features. We conclude that this is a relevant tool in elastin research.
Assuntos
Tecido Elástico/ultraestrutura , Amarelo de Eosina-(YS) , Corantes Fluorescentes , Hematoxilina , Corantes de Rosanilina , Animais , Cartilagem/ultraestrutura , Cães , Amarelo de Eosina-(YS)/administração & dosagem , Corantes Fluorescentes/administração & dosagem , Hematoxilina/administração & dosagem , Microscopia Confocal/métodos , Microscopia de Fluorescência/métodos , Resorcinóis/administração & dosagem , Corantes de Rosanilina/administração & dosagemRESUMO
To study the prevalence of HIV and infections with related transmission patterns, we interviewed and obtained blood samples from 220 injecting drug users (IDUs), sampled by snowballing, from the city of Santos in the state of São Paulo, Brazil, where the estimated number of IDUs (10,000) comprises approximately 2% of the entire population. Seroprevalence of HIV, hepatitis B and C, syphilis, and HTLV (1 and 2) was assessed and compared with that in 197 blood donors from the same city, matched for age and gender. Risk behavior related to HIV was assessed by a standard questionnaire applied to the IDU sample. Univariate and multivariate analyses of the risk factors were performed. Seroprevalences found were 62% for HIV, 75% for HCV, 75% for HBV, 34% for syphilis, and 25% for HTLV (1 and 2) among IDUs, which compare with 0.0%, 2%, 23%, 12%, and 1% for blood donors, respectively. The risk for parenterally transmitted infections in this IDU community was higher than that for sexually transmitted infections (odds ratio for syphilis, 3.57; hepatitis B, 10.0; and hepatitis C, 100). The results of the mutivariate risk analysis showed that daily rate of ID use >5 times/day (OR = 6.73), not changing behavior to avoid AIDS (OR= 3.28), ID use >15 days/month (OR = 2.72), and ID use in the last 2 months (OR = 2.23) were the risk behaviors significantly associated with HIV infection.
Assuntos
Infecções por HIV/epidemiologia , Infecções por HTLV-I/epidemiologia , Infecções por HTLV-II/epidemiologia , Hepatite B/epidemiologia , Hepatite C/epidemiologia , Abuso de Substâncias por Via Intravenosa/complicações , Sífilis/epidemiologia , Adolescente , Adulto , Western Blotting , Brasil/epidemiologia , Cocaína , Transmissão de Doença Infecciosa , Ensaio de Imunoadsorção Enzimática , Feminino , Infecções por HIV/etiologia , Infecções por HIV/transmissão , Infecções por HTLV-I/etiologia , Infecções por HTLV-I/transmissão , Infecções por HTLV-II/etiologia , Infecções por HTLV-II/transmissão , Hepatite B/etiologia , Hepatite B/transmissão , Hepatite C/etiologia , Hepatite C/transmissão , Humanos , Masculino , Pessoa de Meia-Idade , Prevalência , Fatores de Risco , Estudos Soroepidemiológicos , Comportamento Sexual , Inquéritos e Questionários , Sífilis/etiologia , Sífilis/transmissãoRESUMO
Aspects of the molecular organization of the antennal sensilla trichodea of Triatoma infestans have been investigated with the use of both polarization and scanning electron microscopy. The sensilla have a smooth surface with minute bulbs on the tapered end. They showed strong positive birefringence, irrespective of the refractive index of the imbibing medium. The plotting of a form birefringence (FB) curve for native material showed slight increases in the retardation values with increases of the refractive index and at least 2 inflection points. On the other hand, a FB curve constructed for alkali-treated structures reveals higher values for the form birefringence and slight decreases in retardation values with raising refractive index. These results demonstrate that chitin fibrils are preferentially aligned with the sensilla long axis. Interestingly, the alkali treatment introduced no alterations in the retardation values measured at n = 1,435, which corresponds to the intrinsic birefringence of chitin. It is suggested that components removed by alkali-treatment have electronic transitions disposed perpendicularly to the chitin filaments and that the ill definition of the form birefringence curve of chitin is associated with the incomplete removal of chitin-associated components, which keep chitin fibrils apart from but strongly bound to each other. In addition, it is apparent from the results that cross-linking in a system with a parallel array of the chitin fibrils occurs predominantly perpendicular to the chitin fibrils.
Assuntos
Quitina/análise , Triatoma/ultraestrutura , Animais , Birrefringência , Microscopia de Polarização , Triatoma/químicaRESUMO
Elastic system components have been described in the pressure-bearing tendon of the bullfrog, Rana catesbeiana, as a result of histochemical tests and transmission and scanning electron microscopy. The tension region was shown to possess microfibril bundles, some of which exhibited central deposits of amorphous material. The use of ANS-butanol plus fluorescence microscopy enormously facilitated the identification of elastic system components in both tension and compression regions of the frog tendon. The compression region exhibited pre-elastic and mature elastic fibers, which were shown to be associated with the surface of the convoluted collagen bundles. Thin fibrils were observed in the compression region after ANS treatment. The visceral paratenon had an increased number of elastic fibers located between the collagen bundles and close to the cells. Congo red plus polarization microscopy failed to impart birefringence to the elastic fibers, but they could be identified by their intense staining and isotropic appearance against the bright background of birefringent collagen fibers. SEM demonstrated the three-dimensional aspects of the elastic fibers. They are composed of fibrils of a sinuous nature. The use of ruthenium red in the fixative allowed for the observation of an intimate association of proteoglycan granules with the microfibril bundles. The elastic components identified in the pressure-bearing tendon are assumed to be important for the tissue supramolecular organization, especially in the maintenance of the convoluted state of the collagen fibers in the compression region and their crimp morphology in the tension region. The elastic system must also play an important role in the restoration of the resting shape of the tendon after the deformation achieved during mechanical stimulation.
Assuntos
Rana catesbeiana/anatomia & histologia , Tendões/citologia , Animais , Colágeno/análise , Elasticidade , Elastina/análise , Microscopia Confocal , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Pressão , Tendões/fisiologia , Tendões/ultraestruturaRESUMO
A direct analogy with the function of large proteoglycans in articular cartilage has led to the assumption that the presence of such components in tendon fibrocartilages is a major factor enabling these structures to resist pressure. However, the association of collagen fibrils in bundles and their tensional state as verified through the existence of crimp under polarized light in tendon fibrocartilage raises doubts as to whether the large proteoglycans are kept under osmotic pressure, which is an essential condition for their physiological role in articular cartilage. This suggests that tendon fibrocartilage has distinct mechanisms to resist pressure. In tendon fibrocartilages, the compressive forces must be transferred to the inextensible collagen fibers which lie in many directions in different planes, before reaching the parallel fibers of the tension region. In this sense, the large proteoglycans are likely to have the function of providing a viscous and cohesive environment in which collagen fibers could get stretched to reinforce the tissue.
Assuntos
Tendões/fisiologia , Animais , Fenômenos Biomecânicos , Bovinos , Colágeno/fisiologia , Microscopia de Polarização , Proteoglicanas/fisiologia , Tendões/anatomia & histologiaRESUMO
A new approach for the estimation of the Basic Reproduction Ratio R0 for HIV among intravenous drug users (IVDU) is proposed. This approach is based in an adaptation of the models proposed by Ross and Macdonald for vector-borne infections. A straightforward adaptation of Macdonald's model is presented first: biological vectors are replaced by needles and syringes and we consider a homogeneous population of IVDUs; next we present a modified model where several heterogeneities are considered. Some of those heterogeneities are due to intrinsic differences between needles and syringes and biological vectors; others, such as those related to movements of individuals between communities, should apply to both biological vectors and injection apparatuses. An example of the calculations of R0 for a real IVDUs community is presented.
Assuntos
Infecções por HIV/complicações , Infecções por HIV/transmissão , Abuso de Substâncias por Via Intravenosa/complicações , Animais , Vetores de Doenças , Humanos , Malária/complicações , Malária/transmissão , Matemática , Modelos Biológicos , Uso Comum de Agulhas e Seringas/efeitos adversosRESUMO
Some tendons wrap around joints and receive compressive forces besides transferring the tension forces from muscle to bone. These tendons develop a fibrocartilaginous structure which enables them to withstand pressure. This article describes the existence and distribution of microfibrils (or preelastic fibers) in the pressure-bearing tendons of rabbits and dogs by the application of histochemical assays and transmission electron microscopy. Rabbit and dog tendons possess no mature elastic fibers. The rabbit tendon exhibits some response to Weigert's method prior to oxidation which indicates the existence of the so-called elaunin fibers, especially in the pressure zone. Oxidation with peracetic acid or oxone discloses intricate aspects of the oxytalan fiber distribution in both tension and pressure zones of the dog and rabbit tendons. Bundles of 12 nm microfibrils were demonstrated in the rabbit tendon by electron microscopy after fixation in the presence of tannic acid. The existence of preelastic fibers in the pressure-bearing tendons has been neglected and they are assumed to have importance in the microarchitecture of the tissue and in the ability of the tendon to support tension and compression forces.
Assuntos
Tendões/ultraestrutura , Animais , Cães , Elasticidade , Microscopia Eletrônica , Pressão , Coelhos , Especificidade da Espécie , Estresse Mecânico , Tendões/citologia , Tendões/fisiologiaRESUMO
The plantaris longus tendon of the bullfrog Rana catesbeiana has been structurally and histochemically characterized. The tendon has been shown to wrap around the distal tibio-fibular joint, extending into an aponeurosis. The region under the joint exhibits a large cartilaginous pad. In contrast to the mammalian flexor digitorum profundus tendons, the compression region of the frog tendon is not typically fibrocartilaginous but presents a unique arrangement of convoluted collagen bundles and fibers associated with a large amount of glycosaminoglycans. The sulfated nature of the glycosaminoglycans in the compressed region was determined through enzyme susceptibility as well as through CEC procedures. Cells of the modified zone exhibited morphological variation, from fibroblastic to condrocyte-like. Polarized light analysis revealed an intricate array of collagen bundles which crossed the tendon in different directions and connected the tension and compression regions. The ability of the tendon to resist compressive forces is assumed to be due to the large amount of glycosaminoglycans in the modified region as well as to the complex arrangement of collagen bundles in the tendon as a whole.
Assuntos
Tendões/anatomia & histologia , Animais , Fibroblastos/citologia , Fibroblastos/metabolismo , Fíbula , Glicoproteínas/análise , Glicosaminoglicanos/análise , Articulações/anatomia & histologia , Articulações/fisiologia , Masculino , Polissacarídeos/análise , Rana catesbeiana , Estresse Mecânico , Tendões/citologia , Tendões/fisiologia , TíbiaRESUMO
The fiber distribution and ultrastructure in the plantaris longus pressure-bearing tendon of the bullfrog were investigated. The tension region of the tendon showed a predominant parallel distribution of collagen fibers, but three main zones with different crimp parameters were identified with the use of the polarizing microscope. The compression region showed collagen fibers with aspects of disaggregation and were composed of disperse and undulating fibrils. These collagen fibers establish a three-dimensional network but showed a preferential distribution in planes disposed perpendicularly to the tendon's main axis. It is assumed that the convoluted and disaggregated collagen fibers must be distended before exerting any reinforcement on the tissue and that this only occurs after a great deformation of the tendon. Groups of 5-6 fibrils not associated in fibers are also dispersed in the compression region. The tissue is assumed to have a highly viscous fluid nature allowing for the deformation needed for collagen fibrils to reinforce the tendon structure. The convoluted and crimped structure of collagen fibers would be especially useful when the tendon is submitted to the sudden and strong mechanical loading expected to occur during jumping and to provide the tendon with the capacity of great functional deformability necessary for the high amplitude of feet movements attained on jumping and swimming.